1. Field of the Invention
The present invention generally relates to a call-waiting service, and more particularly, to a method for automatically controlling a call-waiting-interruption restriction and a switching system, which can automatically restrict a call-waiting-interruption for a one-side subscriber, when the other-side subscriber communicating with the one-side subscriber is supplied with a call-waiting-interruption restriction service.
2. Description of the Prior Art
A call-waiting service in speech signal communication is widely used by conventional subscribers. And further, data communication such as telematique services including a facsimile is also used by the conventional subscribers, so that the same subscriber is often supplied with both services of the speech signal communication and the data communication.
In this case, it is desired that the call-waiting service be supplied for the speech signal communication, whereas for the data communication, that a call-waiting-interruption by the call-waiting service be restricted to prevent communication data from being destroyed due to a beep sound for the call-waiting interruption being multiplied with the communication data. This way makes it possible to effectively utilize both the call-waiting and data communication services.
To restrict the interruption by the call-waiting service, a call-waiting-interruption restriction service (cancel-call-waiting service) is already in use. For the subscriber supplied with the cancel-call-waiting service, the call-waiting interruption coming from a third subscriber can be restricted during the communication. Therefore, this service can prevent the communication data from being destroyed due to the beep sound for the interruption.
Recently, a duplex ringing (DR) service is also being used. In the DR service, a subscriber connected to one subscriber line is supplied with a plurality of telephone numbers (two presently) with different kinds of calling-bell sounds. For example, a first telephone number is used for the speech signal communication, and a second telephone number is used for the facsimile.
Especially, when the DR service is supplied to the subscriber with the call-waiting service and the call-waiting-interruption restriction service, it is desired that the first telephone number be used for the speech signal communication and have the call-waiting service, and that the second telephone number be used for the facsimile and have the call-waiting-interruption restriction service. Information of the call-waiting service for the first telephone number, and information of the call-waiting-interruption restriction service for the second telephone number are stored in subscriber data associated with each telephone number.
In this case, when the interruption from the third subscriber to a first subscriber occurs, the call-waiting service is performed by referring to the subscriber data of the first subscriber. Therefore, even if the communication which has been started by terminating to the second telephone number is kept with the call-waiting-interruption restriction service, the interruption from the third subscriber may be accepted when the third subscriber has called to the first telephone number, which is supplied with the call-waiting service.
Therefore, when the communication is started by terminating to the second telephone number for the data communication, the call-waiting service is required to be restricted to prevent the communication data from being destroyed due to the beep sound for the interruption. To meet the requirement, when a call for the data communication terminates to the second telephone number, the call-waiting-interruption restriction service is performed by referring to the subscriber data for the second telephone number, and a restriction bit is set in a call-control memory to restrict an interruption call terminating to the first telephone number.
When the call for the data communication terminates to the first telephone number, the restriction bit is not set in the call-control memory, so that the call-waiting service may be performed by referring to the subscriber data of the first telephone number when the interruption call terminates to the first telephone number.
As described above, in the DR service, one subscriber can be simultaneously supplied with both the call-waiting service and the call-waiting-interruption restriction service.
However, in such a conventional call-waiting-interruption restriction service, the interruption call is only restricted for the subscriber supplied with this service. Therefore, even if this service is supplied to the first subscriber, the interruption call to a second subscriber as the opposite subscriber is not restricted when the second subscriber is supplied with the call-waiting service. Therefore, there is a problem that the communication data is destroyed due to the beep sound for the interruption call when the call-waiting-interruption is performed during the data communication such as telematique services.
On the other hand, another method to implement the data communication without the interruption is presented by an article shown in a Japanese Laid-Open Patent Application No. 3-157043. In this method, a device for discriminating the speech signal and the telematique signal is installed in a time-division switching system. And when the interruption call terminates to the subscriber supplied with the call-waiting service, that device monitors the signal within a communication line and discriminates whether the signal is the speech signal or the telematique signal. When the signal is discriminated to be the telematique signal, the call-waiting service is restricted.
However, if the opposite subscriber for the communication is supplied with the call-waiting service, the interruption call to the opposite subscriber cannot be restricted. The problem previously mentioned still remains. In addition, there is another problem that many devices for discriminating are required.